1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70

package toxi.physics.constraints;

import toxi.geom.Sphere;
import toxi.geom.Vec3D;
import toxi.physics.VerletParticle;

/**
 * This class implements a spherical constraint for 3D
 * {@linkplain VerletParticle}s. The constraint can be configured in two ways: A
 * bounding sphere not allowing particles to escape or alternatively does not
 * allow particles to enter the space occupied by the sphere.
 * 
 * @author toxi 16 Mar 2009
 */
public class SphereConstraint implements ParticleConstraint {

    public Sphere sphere;

    public boolean isBoundingSphere;

    public final static boolean INSIDE = true;
    public final static boolean OUTSIDE = false;

    /**
     * Creates a new instance using the sphere definition and constraint mode
     * given.
     * 
     * @param sphere
     *            sphere instance
     * @param isBoundary
     *            constraint mode. Use {@linkplain #INSIDE} or
     *            {@linkplain #OUTSIDE} to specify constraint behaviour.
     */
    public SphereConstraint(Sphere sphere, boolean isBoundary) {
        this.sphere = sphere;
        this.isBoundingSphere = isBoundary;
    }

    /**
     * Creates a new instance using the sphere definition and constraint mode
     * given.
     * 
     * @param origin
     *            sphere origin
     * @param radius
     *            sphere radius
     * @param isBoundary
     *            constraint mode. Use {@linkplain #INSIDE} or
     *            {@linkplain #OUTSIDE} to specify constraint behaviour.
     */
    public SphereConstraint(Vec3D origin, float radius, boolean isBoundary) {
        sphere = new Sphere(origin, radius);
        this.isBoundingSphere = isBoundary;
    }

    /*
     * (non-Javadoc)
     * 
     * @see
     * toxi.physics.constraints.ParticleConstraint#apply(toxi.physics.VerletParticle
     * )
     */
    public void apply(VerletParticle p) {
        boolean isInside = sphere.containsPoint(p);
        if ((isBoundingSphere && !isInside) || (!isBoundingSphere && isInside)) {
            p.set(sphere.add(p.subSelf(sphere).normalizeTo(sphere.radius)));
        }
    }

}